The reactivation of the cell cycle by the C4 protein from BCSTV seems to occur through the induction of RKP, a ubiquitin E3 ligase [67]; recently, the symptom determinant ability of this C4 has been attributed to its capacity to bind CLV1 in the shoot apical meristem [8], although whether the virus will reach this area during a natural infection remains to be determined. This evidence concerns the gene C4A and infection.